JP6787935B2 - Single-layer or double-layer ammonia slip catalyst - Google Patents

Description

The present invention relates to ammonia slip catalysts (ASCs), articles containing ammonia slip catalysts, and methods of producing and using such articles to reduce ammonia slip.

Carbon dioxide combustion in diesel engines, stationary gas turbines, and other systems must be processed to remove nitrogen oxides (NO _x ), including NO (nitric oxide) and NO ₂ (nitrogen dioxide). Exhaust gas is generated and NO is the majority of NO _x formed. NO _x is to cause some human health problems, as well as including smog and formation of acid rain, that some cause adverse environmental effects of known. For both human and environmental impact from NO _X in the exhaust gas to reduce, preferably by a method which does not generate other harmful substances or toxic substances, it is desirable to remove these undesirable components.

Exhaust gases generated in lean burn and diesel engines are generally oxidative. NO _x is selectively reduced using a catalyst and a reducing agent by a method known as selective catalytic reduction (SCR), which converts NO _x into elemental nitrogen (N ₂ ) and water. There is a need. In the SCR method, a gaseous reducing agent, usually anhydrous ammonia, aqueous ammonia, or urea is added to the exhaust gas stream before the exhaust gas comes into contact with the catalyst. The reducing agent is absorbed on the catalyst and NO _X is reduced when the above gas passes through or on the catalytic substrate. In order to maximize the conversion rate of NO _x , it is often necessary to add ammonia in excess of the stoichiometric amount to this gas stream. However, the release of excess ammonia into the atmosphere appears to be harmful to human health and the environment. In addition, ammonia is corrosive, especially in its aqueous form. Condensation of ammonia and water in the downstream region of the exhaust line of the exhaust catalyst can result in a corrosive mixture that can damage the exhaust system. Therefore, the release of ammonia in the exhaust gas should be eliminated. In many conventional exhaust systems, the ammonia oxidation catalyst (also known as the ammonia slip catalyst or "ASC") is an SCR catalyst to remove ammonia from the exhaust by converting the exhaust to nitrogen. It is installed downstream. The use of ammonia slip catalysts allows for NO _x conversion rates in excess of 90% over a typical diesel operating cycle.

A catalyst that achieves both NO _x removal by SCR and selective ammonia conversion to nitrogen, where ammonia conversion takes place over a wide range of temperatures during the vehicle's driving cycle, and nitrogen oxides and dinitrogen monoxide sub. It would be desirable to have a catalyst that minimizes product formation.

In a first aspect, the invention comprises (a) an extrusion-molded carrier having multiple channels through which exhaust gas flows during operation of the engine, and (b) a single-layer or two-layer coating on the carrier. A catalyst article comprising, wherein the extrusion-molded carrier comprises a third SCR catalyst and the monolayer coating comprises a blend of platinum supported on a carrier having low ammonia storage and a first SCR catalyst. The two-layer coating comprises a lower layer and an upper layer, the lower layer is located between the upper layer and the extrusion-molded carrier, and the lower layer is a platinum supported on a carrier having low ammonia storage and a first layer. With respect to a catalytic article comprising a blend with the SCR catalyst of the above, wherein the top layer comprises a second SCR catalyst.

In another aspect, the invention relates to an exhaust system comprising the catalyst of the first aspect of the invention and means for forming NH _{3 in the} exhaust gas.

In yet another aspect, the invention relates to a vehicle comprising an exhaust system with the catalyst of the first aspect of the invention and means for forming NH _{3 in the} exhaust gas.

In yet another aspect, the invention comprises contacting the exhaust gas containing ammonia with the catalytic article of the first aspect of the invention at a temperature of about 250 ° C. to about 350 ° C. from ammonia in the exhaust gas. N ₂ Regarding a method for improving the yield.

In another aspect, the present invention provides a method for reducing the N _{2 O} formed from NH ₃ in the exhaust gas, contacting the exhaust gas containing ammonia in the catalyst article of the first aspect of the present invention Including, regarding methods.

FIG. 6 is a schematic configuration in which a monolayer blend of ammonia slip catalysts is located on both sides of a substrate containing a third SCR catalyst. A two-layer coating having a lower layer containing a mixture of platinum and a first SCR catalyst carried on a low ammonia storage carrier and an upper layer containing a second SCR catalyst contains a third SCR catalyst. It is a schematic diagram of the structure located on both sides of the base material.

As used herein and in the appended claims, the singular forms "a", "an" and "the" include a plurality of indications unless the context expresses otherwise. Thus, for example, a reference to a "catalyst" includes a mixture of two or more catalysts.

As used herein, the term "ammonia slip" means the amount of unreacted ammonia that passes through the SCR catalyst.

The term "carrier" means a material on which the catalyst is immobilized.

The term "carrier with low ammonia storability" means a carrier that stores less than 0.001 mmol of NH ₃ per 1 m ^{3 of} carrier. Carriers with low ammonia storage are preferably AEI, ANA, ATS, BEA, CDO, CFI, CHA, CON, DDR, ERI, FAU, FER, GON, IFR, IFW, IFY, IHW, IMF, IRN, IRY, ISV, ITE, ITG, ITN, ITR, ITW, IWR, IWS, IWV, IWW, JOZ, LTA, LTF, MEL, MEP, MFI, MRE, MSE, MTF, MTN, MTT, MTW, MVY, MWW, NON, NSI, RRO, RSN, RTE, RTH, RUT, RWR, SEW, SFE, SFF, SFG, SFH, SFN, SFS, SFV, SGT, SOD, SSF, SSO, SSY, STF, STO, STT, SVR, A molecular sieve or zeolite having a framework type selected from the group consisting of SVV, TON, TUN, UOS, UOV, UTL, UWY, VET, VNI. More preferably, the molecular sieve or zeolite has a framework type selected from the group consisting of BEA, CDO, CON, FAU, MEL, MFI and MWW, and even more preferably the framework type is BEA. And selected from the group consisting of MFI.

The term "firing" or "firing" means heating a material in air or oxygen. This definition is consistent with the definition of IUPAC for firing (IUPAC. Compendium of Chemical Terminology, 2nd Edition (“Gold Book”). Edited by AD McNaught and A. Wilkinson, Blackwell Scientific Publications, Oxford (1997). XML Modified on-line: http://goldbook.iupac.org (2006-), created by M. Nic, J. Jirat, B. Kosata; edited and updated by A. Jenkins, ISBN 0-9678550-9 -8. doi: 10.1351 / goldbook.). The calcination is carried out to decompose the metal salt and promote the exchange of metal ions in the catalyst, and also to attach the catalyst to the substrate. The temperature used for firing depends on the constituents in the material to be fired and is generally between about 1 to 8 hours and between about 400 ° C and about 900 ° C. In some cases, firing can be carried out at temperatures up to about 1200 ° C. In applications including the methods described herein, firing is generally at a temperature of about 1 to 8 hours, about 400 ° C to about 700 ° C, preferably about 1 to 4 hours, about 400 ° C. It is carried out at a temperature of about 650 ° C.

The term "about" means approximately, optionally ± 25%, preferably ± 10%, more preferably ± 5%, or most preferably ± 25% of the value to which the term relates. Refers to the range of ± 1%.

If a range (s) for various numbers of elements are presented, the range (s) may include that value, unless otherwise specified.

The term "N ₂ selectivity" means the conversion rate of ammonia to nitrogen.

In a first aspect of the invention, the catalytic article is (a) an extrusion-molded carrier having multiple channels through which exhaust gas flows during inlet, outlet, and engine operation, and (b) a monolayer coating on the carrier. Alternatively, the extruded carrier comprises a two-layer coating, the extruded carrier comprises a third SCR catalyst, and the monolayer coating comprises a blend of platinum carried on a carrier with low ammonia storage and a first SCR catalyst. The layer coating includes a lower layer and an upper layer, the lower layer is located between the upper layer and the extrusion-molded carrier, and the lower layer is a platinum supported on a carrier having low ammonia storage and a first layer. It contains a blend with an SCR catalyst and the top layer contains a second SCR catalyst. The carrier having low ammonia storage capacity can be a siliceous carrier, and the siliceous carrier is silica, or ≧ 100, preferably ≧ 200, more preferably ≧ 250, even more preferably ≧ 300, especially ≧ 400, Zeolites having a silica-to-alumina ratio of more particularly ≧ 500, even more particularly ≧ 750, and most preferably ≧ 1000 can be included. Silica carriers include BEA, CDO, CON, FAU, MEL, MFI or MWW. The catalyst article, as compared with a catalyst comprising a comparison formulation, it is possible to realize the improvement of the N ₂ yield from ammonia at a temperature from about 250 ° C. to about 300 ° C., in this case, the first SCR catalyst Is present as the first layer, platinum supported on the siliceous carrier is present in the second layer, and the gas containing NH ₃ passes through the first layer before passing through the second layer. To do. The catalyst article can protect platinum from one or more substances present in the catalyst that can poison platinum, such as vanadium. The catalyst article can protect platinum from other poisons such as potassium, sodium, iron and tungsten. When the first SCR catalyst contains vanadium, the catalyst article can achieve reduced deactivation as compared to a catalyst containing a comparative formulation, in which case the first SCR catalyst is the first layer. Platinum supported on the siliceous carrier is present in the second layer, and the gas containing NH ₃ passes through the first layer before passing through the second layer.

The term "supporting amount of active component" refers to the weight of the platinum carrier in the blend + the weight of platinum + the weight of the first SCR catalyst. Platinum is from about 0.01 to about 0.3% by weight (including both ends), preferably from about 0.03 to 0.2% by weight (including both ends), more preferably from about 0.05 to 0.17% by weight. % (Including both ends), most preferably from about 0.07 to 0.15% by weight (including both ends), can be present in the catalyst in an amount carrying an active component.

Additional catalysts such as palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru) or rhodium (Rh) can be present with Pt, preferably in a blend containing Pt.

SCR catalyst In various embodiments, the composition may include one, two or three SCR catalysts. The first SCR catalyst, which is always present in the composition, is (1) in a blend containing Pt supported on a carrier having low ammonia storage, or (2) the catalyst is present in two layers. If Pt is present in the lower layer, it can be present in either one of the upper layers. The first SCR catalyst is preferably Cu-SCR catalyst or Fe-SCR catalyst or mixed oxide, more preferably a Cu-SCR catalyst or mixed oxide, and most preferably Cu-SCR catalyst. Cu-SCR catalysts include copper and molecular sieves. Fe-SCR catalysts include iron and molecular sieves. Molecular sieves are further described below. The molecular sieve can be aluminosilicate, aluminophosphate (AlPO), silico-aluminophosphate (SAPO), or a mixture thereof. Copper or iron can be located within the framework of the molecular sieve and / or in (replaceable) sites outside the framework within the molecular sieve.

The second and third SCR catalysts can be the same or different. The second and third SCR catalysts can be base metals, oxides of base metals, noble metals, molecular sieves, metal exchanged molecular sieves or mixtures thereof. Base metals are vanadium (V), molybdenum (Mo), tungsten (W), chromium (Cr), cerium (Ce), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and copper ( It can be selected from the group consisting of Cu) and mixtures thereof. SCR compositions consisting of vanadium supported on refractory metal oxides such as alumina, silica, zirconia, titania, cerium oxide and combinations thereof are well known and are widely used commercially in mobile applications. Typical compositions are described in US Pat. Nos. 4010238 and 4085193, the entire contents of which are incorporated herein by reference. In particular, in mobile applications, the commercially used composition is TiO ₂ , on which WO ₃ and V ₂ O ₅ are 5 to 20% by weight and 0.5 to 6% by weight, respectively. Includes TiO ₂ dispersed in a range of concentrations. The second SCR catalyst may include Ce-Zr or promoter Sorted MnO ₂ which is promotion bets. Preferably, the promoter comprises Nb. The noble metal can be platinum (Pt), palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru) or rhodium (Rh), or a mixture thereof. These catalysts may contain other inorganic substances such as SiO ₂ and ZrO _{2 that} act as binders and promoters.

If the SCR catalyst is a base metal, the catalyst article may further comprise at least one base metal promoter. As used herein, it is understood that "promoter" means a substance that, when added to a catalyst, enhances the activity of the catalyst. Base metal promoters can be in the form of metals, metal oxides, or mixtures thereof. At least one base metal catalytic promoter is neodymium (Nd), barium (Ba), cerium (Ce), lanthanum (La), praseodymium (Pr), magnesium (Mg), calcium (Ca), manganese (Mn), zinc ( It may be selected from Zn), niobium (Nb), zirconium (Zr), molybdenum (Mo), tin (Sn), tantalum (Ta), strontium (Sr) and oxides thereof. The at least one base metal catalytic promoter can preferably be MnO ₂ , Mn ₂ O ₃ , Fe ₂ O ₃ , SnO ₂ , CuO, CoO, CeO ₂ and mixtures thereof. At least one base metal catalyst promoter may be added to the catalyst in the form of a salt in aqueous solution, such as nitrate or acetate. At least one base metal catalyst and at least one base metal catalyst, such as copper, may be impregnated from the aqueous solution onto the oxide carrier material, added to a washcoat containing the oxide carrier material, or by washcoat. It may be impregnated with a pre-coated carrier.

The SCR catalyst can include a molecular sieve or a metal exchanged molecular sieve. As used herein, "molecular sieve" is understood to mean a metastable material containing small pores of precise and uniform size that can be used as an adsorbent for gases or liquids. .. Molecules that are small enough to pass through the pores are adsorbed, while larger molecules are not. The molecular sieve can be a zeolite-based molecular sieve, a non-zeolitic molecular sieve, or a mixture thereof.

Zeolitic molecular sieves are microporous aluminosilicates having any one of the framework structures listed in the Database of Zeolites Structures published by the International Zeolite Association (IZA). is there. Framework structures include, but are not limited to, CHA, FAU, BEA, MFI, and MOR types. Non-limiting examples of zeolites having these structures include chavasite, faujasite, zeolite Y, ultrastable zeolite Y, beta zeolite, mordenite, silicalite, zeolite X, and ZSM-5. Aluminosilicate zeolites have a useful range from about 10 to 200, from at least about 5, preferably at least about 20, a silica / alumina molar ratio defined as SiO ₂ / Al ₂ O _3. ratio: SAR) can be provided.

Any of the SCR catalysts can include small pores, medium pores or large pore molecular sieves, or mixtures thereof. A "small pore molecular sieve" is a molecular sieve containing the maximum ring size of eight tetrahedral atoms. A "medium pore molecular sieve" is a molecular sieve containing the maximum ring size of 10 tetrahedral atoms. A "large pore molecular sieve" is a molecular sieve having a maximum ring size of 12 tetrahedral atoms. The second and / or third SCR catalysts are aluminosilicate molecular sieves, metal-substituted aluminosilicate molecular sieves, aluminophosphate (AlPO) molecular sieves, metal-substituted aluminosilicate (MeAlPO) molecular sieves, silico-aluminophosphates. Can include small pore molecular sieves selected from the group consisting of salt (SAPO) molecular sieves, and metal-substituted silico-aluminosilicate (MeAPSO) molecular sieves, as well as mixtures thereof.

All of the SCR catalysts are ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, and ZON, and their mixtures and / or It can include small pore molecular sieves selected from the group of framework types consisting of intergrowth. Preferably, the small pore molecular sieve is selected from the group of framework types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR and ITE.

All of the SCR catalysts are AEL, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR, JST, LAU, LOV, MEL, MFI, MFS, MRE, MTT, MVY, MWW, NAB, NAT, NES, OBW, PAR, PCR, PON, PUN, RRO, RSN, SFF, SFG, STF, STI, STT, STW, -SVR, SZR, TER, TON , TUN, UOS, VSV, WEI, and WEN, and mixtures and / or intergrowths thereof, can include medium pore molecular sieves selected from the group of framework types. Preferably, the medium pore molecular sieve is selected from the group of framework types consisting of MFI, FER and STT.

All of the SCR catalysts are AFI, AFR, AFS, AHY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON, CZP, DFO, EMT, EON, EZT, FAU, GME, GON, IFR, ISV, ITG, IWR, IWS, IWV, IWW, JSR, LTF, LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, OSI, RON, RWY, SAF, SAO, SBE, Selected from a group of framework types consisting of SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STO, SSF, SSY, USI, UWY, and VET, and mixtures and / or intergrowths thereof. Can include large pore molecular sieves. Preferably, the large pore molecular sieve is selected from the group of framework types consisting of MOR, OFF and BEA.

The molecular sieves in the Cu-SCR and Fe-SCR catalysts are ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI. , GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, ZON , BEA, MFI and FER, and mixtures and / or intergrowths thereof are preferably selected. More preferably, the molecular sieves in Cu-SCR and Fe-SCR are AEI, AFX, BEA, CHA, DDR, ERI, FER, ITE, KFI, LEV, MFI and SFW, and mixtures and / or twin crystals thereof. Selected from the group consisting of.

The metal exchanged molecular sieves are deposited on the outer surface of the molecular sieve, or on an extra framework site within its channel, cavity or cage, of the Periodic Table VB, VIB, VIIB, VIIIB, IB, or IIB. It can have at least one metal from one of them. The metal may be in one of several forms, including, but not limited to, zero-valent metal atoms or clusters, isolated cations, mononuclear or polynuclear oxycations, or widespread metal oxides. May exist as. Preferably, the metal can be iron, copper, and mixtures or combinations thereof.

The metal can be mixed with the zeolite in a suitable solvent using a mixture or solution of metal precursors. The term "metal precursor" means any compound or complex that can be dispersed on a zeolite to provide a catalytically active component of the metal. Preferably, the solvent is water because of both the economic and environmental aspects of using other solvents. When copper, the preferred metal, is used, suitable complexes or compounds are, but are not limited to, copper sulphate, copper nitrate, copper acetate, acetyl copper acetate, copper oxide, copper hydroxide, and salts of copper amines ( For example, it contains an anhydride or hydrate of [Cu (NH ₃ ) ₄ ] ²⁺ ). The present invention is not limited to metal precursors of a particular type, composition or purity. The molecular sieve can be added to a solution of the metal constituents to form a suspension, which is then reacted to distribute the metal constituents on the zeolite. The metal can be distributed in the pore channels of the molecular sieve and on its outer surface. The metal can be distributed in ionic form or as a metal oxide. For example, copper can be distributed as copper (II) ions, copper (I) ions, or as copper oxide. The metal-containing molecular sieve can be separated from the liquid phase of the suspension and washed and dried. Next, the obtained metal-containing molecular sieve can be calcined to fix the metal in the molecular sieve. Preferably, the second and third catalyst, Cu-SCR catalyst containing copper and molecular sieve, Fe-SCR catalyst containing iron and molecular sieves, catalysts based on vanadium, promoter Sorted Ce-Zr or promotion including the door has been MnO _2.

The metal exchanged molecular sieve is located on the outer surface of the molecular sieve, or on an extra framework site within its channel, cavity or cage, in the range of about 0.10% by weight and about 10% by weight, VB, It can contain VIB, VIIB, VIIIB, IB, or Group IIB metals. Preferably, the extra framework metal can be present in an amount in the range of about 0.2% by weight and about 5% by weight.

The metal exchanged molecular sieve is a copper (Cu) or iron (Fe) -supported small pore molecular sieve having about 0.1 to about 20.0 wt% of the total weight of the catalyst. Can be. More preferably, copper or iron is present in about 0.5% to about 15% by weight of the total weight of the catalyst. Most preferably, copper or iron is present in about 1% to about 9% by weight of the total weight of the catalyst.

The first SCR catalyst can be a Cu-SCR catalyst containing copper and small pore molecular sieves, or an Fe-SCR catalyst containing iron and small pore molecular sieves. The small pore molecular sieve can be an aluminosilicate, an aluminophosphate (AlPO), a silico-aluminophosphate (SAPO), or a mixture thereof. Small pore molecular sieves are ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE. , ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, and ZON, and their mixtures and / Alternatively, it can be selected from a group of framework types consisting of intergrowths. Preferably, the small pore molecular sieve can be selected from the group of framework types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR and ITE. The ratio of the amount of the first SCR catalyst to the amount of platinum supported on the carrier having low ammonia storage is (a) 0: 1 to 300: 1, (b) based on the weight of these components. ) Can be in the range of 3: 1 to 300: 1, (c) 7: 1 to 100: 1, and (d) 10: 1 to 50: 1 (including both ends). Platinum is (a) 0.01-0.3% by weight and (b) 0.03-0.2 with respect to the weight of the platinum carrier in the blend + the weight of platinum + the weight of the first SCR catalyst. It can be present in at least one of% by weight, (c) 0.05-0.17% by weight, and (d) 0.07-0.15% by weight (including both ends).

The second SCR catalyst and the third SCR catalyst can independently be a base metal, a base metal oxide, a molecular sieve, a metal-exchanged molecular sieve, or a mixture thereof. Base metals are vanadium (V), molybdenum (Mo), tungsten (W), chromium (Cr), cerium (Ce), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper. It can be selected from the group consisting of (Cu) and mixtures thereof. The catalyst article may further comprise at least one base metal promoter. The molecular sieve or metal-exchanged molecular sieve can be small pores, medium pores, large pores or a mixture thereof. The second and / or third SCR catalysts are aluminosilicate molecular sieves, metal-substituted aluminosilicate molecular sieves, aluminophosphate (AlPO) molecular sieves, metal-substituted aluminosilicate (MeAlPO) molecular sieves, silico-aluminophosphates. Can include small pore molecular sieves selected from the group consisting of salt (SAPO) molecular sieves, and metal-substituted silico-aluminosilicate (MeAPSO) molecular sieves, as well as mixtures thereof. The second and / or third SCR catalysts are ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, and ZON, and Small pore molecular sieves selected from the group of framework types consisting of mixtures and / or intergrowths thereof can be included. The second and / or third SCR catalyst preferably comprises a small pore molecular sieve selected from the framework type group consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR and ITE. Can be done. The second and / or third SCR catalysts are AEL, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR, JST, LAU, LOV, MEL, MFI, MFS, MRE, MTT, MVY, MWW, NAB, NAT, NES, OBW, -PAR, PCR, PON, PUN, RRO, RSN, SFF, SFG, STF, STI, STT, STW, SVR , SZR, TER, TON, TUN, UOS, VSV, WEI, and WEN, and medium pore molecular sieves selected from the group of framework types consisting of mixtures and / or intergrowths thereof. The second and / or third SCR catalysts are AFI, AFR, AFS, AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON, CZP, DFO, EMT, EON, EZT, FAU, GME, GON, IFR, ISV, ITG, IWR, IWS, IWV, IWW, JSR, LTF, LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, OSI, -RON, RWY , SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STO, SSF, SSY, USI, UWY, and VET, and their mixtures and / or flanking frames. It preferably comprises a large pore molecular sieve selected from the work type group. The third SCR catalyst preferably comprises a vanadium, Fe zeolite, Cu zeolite, or a Ce—Zr-based catalyst doped with Fe, W or Nb.

The catalysts described herein can be used for SCR treatment of exhaust gases from various engines. The engine can relate to a vehicle, a stationary engine, an engine in a power plant, or a gas turbine. One of the properties of a catalyst comprising a blend of platinum supported on a siliceous carrier and a first SCR catalyst, wherein the first SCR catalyst is a Cu-SCR catalyst or a Fe-SCR catalyst, comprises a comparative formulation. compared with the catalyst, is that it is possible to realize improvement of N ₂ yield from ammonia at a temperature from about 250 ° C. to about 350 ° C., in this case, the first SCR catalyst is present as a first layer Platinum is supported on a layer that stores ammonia and is present in the second layer, and the gas containing NH ₃ passes through the first layer before passing through the second layer. Another property of the catalyst, which comprises a blend of platinum carried on a carrier having low ammonia storage and a first SCR catalyst, wherein the first SCR catalyst is a Cu-SCR catalyst or a Fe-SCR catalyst, is a comparative formulation. compared with a catalyst comprising an object is that it is possible to realize a reduction in N _{2 O} formed from NH _3, in this case, the first SCR catalyst is present as a first layer, platinum ammonia Supported on a storage carrier, present in the second layer, the gas containing NH ₃ passes through the first layer before passing through the second layer.

The catalyst substrate is any material commonly used to prepare automotive catalysts, including honeycomb structures, extrusion carriers, metal substrates, or flow-through or filter structures such as SCRF. May be good. Preferably, the substrate has a plurality of parallel fine gas flow passages extending from the inlet surface to the outlet surface of the substrate so that the passages are open and the fluid flows. Such monolith carriers can contain up to about 700 or more flow paths (or "cells") per square inch of cross-sectional area, but significantly fewer may be used. For example, the carrier may have about 7 to 600 cells per square inch (“cpsi”), and more generally about 100 to 400 cells. The passage, which is a substantially straight path from those fluid inlets to those fluid outlets, is a wall on which the SCR catalyst is coated as a "washcoat" so that the gas flowing through the passages is the catalyst. Defined by the above wall in contact with the material. The flow path of the monolithic substrate is a thin wall channel that can have any suitable cross-sectional shape such as trapezoid, rectangle, quadrangle, triangle, sinusoid, hexagon, ellipse, circle. The present invention is not limited to a particular substrate type, material, or shape.

Ceramic substrates are cordierite, cordierite-α-alumina, α-alumina, silicon carbide, silicon nitride, zirconia, mullite, spodium, alumina-silica magnesia, zirconium silicate, silimanite, magnesium silicate, zircon, petalite. , Aluminosilicates and mixtures thereof, can be made from any suitable refractory material.

The wall flow substrate may also be formed from a ceramic fiber composite, such as one formed from cordierite and silicon carbide. Such materials are capable of withstanding the environments faced when treating the exhaust stream, especially the high temperatures.

The base material can be a highly porous base material. The term "highly porous substrate" refers to a substrate having a porosity between about 40% and about 80%. The highly porous substrate can preferably have a porosity of at least about 45%, more preferably at least about 50%. The highly porous substrate can preferably have a porosity of less than about 75%, more preferably less than about 70%. The term porosity, as used herein, refers to total porosity, preferably measured using a mercury porosimeter.

Preferably, the substrate can be a cordierite, a highly porous cordierite, a metal substrate, an extruded SCR, a filter or an SCRF.

A washcoat comprising a blend of platinum supported on a siliceous carrier and a first SCR catalyst, wherein the first SCR catalyst is preferably a Cu-SCR catalyst or an Fe-SCR catalyst, is a method known in the art. Can be applied to the inlet side of the substrate using. After applying the washcoat, the composition can be dried and sintered. If the composition comprises a second SCR, the second SCR can be applied to the fired article having a lower layer with separate washcoats, as described above. After the second washcoat has been applied, the washcoat can be dried and fired, as was done for the first layer.

The layer-containing platinum-containing substrate can be dried and calcined at temperatures in the range of 300 ° C. to 1200 ° C., preferably 400 ° C. to 700 ° C., and more preferably 450 ° C. to 650 ° C. .. Firing is preferably carried out under dry conditions, but can also be carried out with hot water, i.e. in the presence of some moisture content. Baking can be carried out between about 30 minutes and about 4 hours, preferably between about 30 minutes and about 2 hours, more preferably between about 30 minutes and about 1 hour.

The exhaust system can include the catalyst of the first aspect of the invention and means for forming NH _{3 in the} exhaust gas. The exhaust system further comprises a second catalyst selected from the group consisting of a diesel oxidation catalyst (DOC), a diesel exothermic catalyst (DEC), a filter-supported selective catalytic reduction (SCRF) or a catalyzed soot filter (CSF). The second catalyst is located downstream of the catalyst of the first aspect of the present invention. The exhaust system includes SCR catalyst, filter-supported selective catalytic reduction (SCRF), diesel oxidation catalyst (DOC), diesel exothermic catalyst (DEC), NOx absorber catalyst (NAC) (lean NOx trap (LNT), NAC, passive NOx). A second catalyst, selected from the group consisting of an adsorber (PNA), etc.), a catalyzed soot filter (CSF), or a cold start concept (CSC) catalyst, can further be provided, wherein the second catalyst is the present invention. It is located upstream of the catalyst of the first aspect of.

The exhaust system can include the catalyst of the first aspect of the present invention, the SCR catalyst and the DOC catalyst, and the SCR catalyst is located between the catalyst of the first aspect of the present invention and the DOC catalyst. The exhaust system can be equipped with a platinum group metal in front of the SCR catalyst, and the amount of platinum group metal is sufficient to generate heat. Exhaust system may include located downstream of the catalyst of the first aspect of the present invention, the MnO ₂ which is Ce-Zr or promoter bets are promoter bets further.

The engine can include the exhaust system described above. The engine can be a vehicle engine, a stationary engine, a power plant engine, or a gas turbine.

The vehicle may be equipped with an exhaust system comprising the catalyst of the first aspect of the invention and means for forming NH _{3 in the} exhaust gas. The vehicle can be a car, a light truck, a heavy truck or a boat.

At a temperature from about 250 ° C. to about 300 ° C., a method of improving the N ₂ yield from ammonia in the exhaust gas comprises contacting an exhaust gas containing ammonia in the catalyst of the first aspect of the present invention. The yield improvement can be from about 10% to about 20% compared to the catalyst containing the comparative formulation, in which case the first SCR catalyst is present as the first layer. The siliceous carrier-supported platinum is present in the second layer, and the gas containing NH ₃ passes through the first layer before passing through the second layer.

Method of reducing the N _{2 O} formed from NH ₃ in the exhaust gas comprises contacting an exhaust gas containing ammonia in the catalyst of the first aspect of the present invention. Reduction of N 2 _O formation, as compared with a catalyst comprising a comparison formulation, it is possible to from about 20% to about 40%, in this case, the first SCR catalyst is present as a first layer The siliceous carrier-supported platinum is present in the second layer, and the gas containing NH ₃ passes through the first layer before passing through the second layer.

The following examples merely illustrate the present invention. Those skilled in the art are aware of a number of variations within the spirit of the invention and claims.

Example 1: Selective ASC on extruded SCR catalyst
The extruded SCR catalyst containing vanadium is coated from the outlet side with a washcoat containing a blend of platinum and Cu-CHA supported on a carrier with low ammonia storage.

Example 2: Selective ASC on extruded SCR catalyst
The extruded SCR catalyst containing Fe-zeolite is coated from the outlet side with a washcoat, including a blend of platinum and Cu-CHA supported on a carrier with low ammonia storage.

Compared to conventional single-layer ASCs, where the single-layer coating contains platinum supported on a carrier such as alumina and does not contain any SCR catalyst in the coating, the ASCs described herein are N. _{2 It} results in reduced selectivity for both O and NOx. This results in improved selectivity for N ₂ over a sufficient temperature range.

Example 3: Selective ASC on Extruded SCR Catalyst
The vanadium-containing extruded SCR catalyst is coated from the outlet side with a platinum-containing washcoat supported on a carrier with low ammonia storage to form a lower layer. A second washcoat containing Cu-CHA is placed on top of the lower layer to form the upper layer.

Example 4: Selective ASC on Extruded SCR Catalyst
The extruded SCR catalyst containing Fe-zeolite is coated from the outlet side with a platinum-containing washcoat supported on a carrier having low ammonia storage to form a lower layer. A second washcoat containing Cu-CHA is placed on top of the lower layer to form the upper layer.

Lower coating, for example, comprises an alumina supported platinum, top coating comprises an SCR catalyst, as compared to conventional two-layer ASC, ASC as described herein, N 2 _O and both the selectivity of NOx Brings a decrease in. This results in improved selectivity for N ₂ over a sufficient temperature range. Further, since the entire coating layer is thinner, the back pressure is reduced.

In the above examples, platinum is supported on a carrier having low ammonia storability. The use of carriers with low ammonia storability helps protect platinum from exposure to substances such as vanadium that can poison or adversely affect platinum.

Example 5: SCRF with ASC
The SCRF filter is coated on the outlet surface of the filter having a platinum-containing washcoat supported on a carrier having low ammonia storage to form a lower layer. A second washcoat containing Cu-CHA is placed on top of the lower layer to form the upper layer.

Example 6: SCRF with ASC
The SCRF filter is coated on the outlet surface of a filter having a washcoat containing a blend of platinum and Cu-CHA supported on a carrier with low ammonia storage.

SCRFs with ASCs in Examples 5 and 6 achieve the same results and benefits as described for Examples 1-4.

The aforementioned examples are intended merely as an example, and the following claims define the scope of the present invention.

Claims (33)

NO _X removal and nitrogen by SCR, including (a) an extrusion-molded carrier with multiple channels through which exhaust gas flows during engine operation, and (b) single-layer or double-layer coating on the carrier. A catalytic article for selective ammonia conversion to, where the single layer coating comprises a blend of platinum supported on a siliceous carrier and a first SCR catalyst, and the two layer coating is the lower and upper layers. The lower layer is located between the upper layer and the extrusion-molded carrier, the lower layer contains a blend of platinum supported on the siliceous carrier and the first SCR catalyst, and the upper layer A catalyst article comprising a second SCR catalyst and the extrusion-molded carrier comprising a third SCR catalyst. Silica carriers are silica, or (a) at least 100, (b) at least 200, (c) at least 250, at least 300, (d) at least 400, (e) at least 500, (f) at least 750 and (g). The catalyst article of claim 1 , comprising a zeolite having at least one silica to alumina ratio of at least 1000. The catalytic article of claim 1 , wherein the siliceous carrier comprises BEA, CDO, CON, FAU, MEL, MFI or MWW. The ratio of the amount of the first SCR catalyst to the amount of platinum carried on the siliceous carrier is (a) 0: 1 to 300: 1, (b) 3: 3 based on the weight of these components. The catalytic article according to claim 1, which is in the range of at least one of 1 to 300: 1, (c) 7: 1 to 100: 1, and (d) 10: 1 to 50: 1 (including both ends). .. The catalyst article according to claim 1, wherein the first SCR catalyst is a Cu-SCR catalyst containing copper and small pore molecular sieves, an Fe-SCR catalyst containing iron and small pore molecular sieves, or a mixed oxide . .. The catalyst article according to claim 5 , wherein the small pore molecular sieve is an aluminosilicate, an aluminophosphate (AlPO), a silico-aluminophosphate (SAPO), or a mixture thereof. Small pore molecular sieves are ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE. , ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, and ZON, and their mixtures and / The catalyst article according to claim 5 , which is selected from the group of framework types consisting of intergrowth crystals. The catalytic article of claim 5 , wherein the small pore molecular sieve is selected from the group of framework types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR and ITE. Platinum is (a) 0.01-0.3% by weight and (b) 0.03-0.2 based on the weight of the platinum carrier in the blend + the weight of platinum + the weight of the first SCR catalyst. The catalyst article according to claim 1, which is present in at least one of (c) 0.05-0.17% by weight and (d) 0.07-0.15% by weight (including both ends). .. The catalyst article according to claim 1, wherein the second SCR catalyst and the third SCR catalyst are a base metal, a base metal oxide, a molecular sieve, a metal-exchanged molecular sieve, or a mixture thereof, independently of each other. .. Base metals are vanadium (V), molybdenum (Mo), tungsten (W), chromium (Cr), cerium (Ce), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper. The catalyst article according to claim 10 , which is selected from the group consisting of (Cu) and a mixture thereof. The catalytic article of claim 10 , further comprising at least one base metal promoter. The catalyst article according to claim 10 , wherein the molecular sieve or the metal-exchanged molecular sieve is a small pore, a medium pore, a large pore, or a mixture thereof. The second and / or third SCR catalysts are aluminosilicate molecular sieves, metal-substituted aluminosilicate molecular sieves, aluminosilicate (AlPO) molecular sieves, metal-substituted aluminosilicate (MeAlPO) molecular sieves, silico-aluminophosphates. The catalytic article of claim 10 , comprising a small pore molecular sieve selected from the group consisting of a salt (SAPO) molecular sieve, a metal-substituted silico-aluminosilicate (MeAPSO) molecular sieve, and a mixture thereof. The second and / or third SCR catalysts are ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, and ZON, and The catalytic article of claim 14 , comprising a small pore molecular sieve, selected from the group of framework types consisting of mixtures and / or intergrowths thereof. Claimed that the second and / or third SCR catalyst comprises a small pore molecular sieve selected from the group of framework types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR and ITE. Item 14. The catalyst article according to Item 14 . The second and / or third SCR catalysts are AEL, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR, JST, LAU, LOV, MEL, MFI, MFS, MRE, MTT, MVY, MWW, NAB, NAT, NES, OBW, PAR, PCR, PON, PUN, RRO, RSN, SFF, SFG, STF, STI, STT, STW, SVR, SZR, TER, TON, TUN, UOS, VSV, WEI, and WEN, and is selected from the group of framework type mixtures thereof and / or intergrowth, including medium pore molecular sieve, to claim 14 The catalyst article described. The second and / or third SCR catalysts are AFI, AFR, AFS, AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON, CZP, DFO, EMT, EON, EZT, FAU, GME, GON, IFR, ISV, ITG, IWR, IWS, IWV, IWW, JSR, LTF, LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, OSI, RON, RWY, A framework consisting of SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STO, SSF, SSY, USI, UWY, and VET, and mixtures and / or twin crystals thereof. The catalytic article of claim 14 , comprising a large pore molecular sieve, selected from the group of types. The catalyst article according to claim 1, wherein the third SCR catalyst comprises a catalyst based on vanadium, Fe zeolite, Cu zeolite, or Ce-Zr doped with Fe, W, or Nb. The catalyst article according to claim 1, wherein the platinum is protected from poisoning action from a substance that can poison one or more platinums present in the catalyst. The catalyst article according to claim 20 , wherein the substance capable of poisoning platinum is vanadium. An exhaust system comprising the means for forming NH ₃ in the catalyst article and exhaust gas according to claim 1. It further comprises a second catalyst selected from the group consisting of a diesel oxidation catalyst (DOC), a diesel exothermic catalyst (DEC), a filter-supported selective catalytic reduction (SCRF), or a catalyzed soot filter (CSF). 22. The exhaust system of claim 22 , wherein the catalyst is located downstream of the catalyst article of claim 1. SCR catalyst, diesel oxidation catalyst (DOC), diesel exothermic catalyst (DEC), NOx adsorber catalyst (NAC) (lean NOx trap (LNT), NAC, passive NOx adsorber (PNA), etc.), Catalyzed soot filter (CSF) The catalyst article according to claim 1, further comprising a second catalyst, selected from the group consisting of filter-supported selective catalytic reduction (SCRF), or cold start concept (CSC) catalysts. The exhaust system according to claim 22 , which is located upstream. An exhaust system comprising the catalyst article , SCR catalyst and DOC catalyst according to claim 1, wherein the SCR catalyst is located between the catalyst article according to claim 1 and the DOC catalyst. 22. The exhaust system according to claim 22 , wherein the platinum group metal is provided in front of the SCR catalyst, and the amount of the platinum group metal is sufficient to generate heat generation. It located downstream of the catalytic article of claim 1, further comprising a MnO ₂ which is Ce-Zr or promoter bets are promotion preparative An exhaust system according to claim 26. An engine comprising the exhaust system according to claim 22 . 28. An engine according to claim 28 , which is an engine in a vehicle, a stationary engine, an engine in a power plant, or a gas turbine. A vehicle comprising the exhaust system according to claim 22 . The vehicle according to claim 30 , which is an automobile, a light truck, a heavy truck or a boat. From about 250 ° C. A method of improving the N ₂ yield from ammonia in the exhaust gas at a temperature of about 300 ° C., comprising contacting the exhaust gas containing ammonia in the catalyst article of claim 1 ,Method. A method for reducing the N _{2 O} formed from NH ₃ in the exhaust gas, comprising contacting the exhaust gas containing ammonia in the catalyst article of claim 1, method.

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